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오늘 본 자료
CALIBRATION OF STELLAR PARAMETERS OF 85 PEG SYSTEM
Bach, Kiehunn,Kim, Yong-Cheol,Demarque, Pierre The Korean Space Science Society 2007 Journal of Astronomy and Space Sciences Vol.24 No.1
We have investigated the evolutionary status of 85 Peg within the framework of standard evolutionary theory. 85 Peg has been known to be a visual and spectroscopic binary system in the solar neighborhood. In spite of the accurate information of the total mass (${\sim}1.5M_{\odot}$) and the distance (${\sim}12pc$) from the HIPPARCOS parallax, it has been undetermined an individual mass, therefore the evolved status of the system. Moreover, the coupled uncertainties of chemical composition and age, make matters worse in predicting an evolutionary status of the system. Nevertheless, we computed the various possible models for 85 Peg, and then calibrated stellar parameters by adjusting to the recent observational data. Our modelling computation has included recently updated input physics and stellar theory such as opacity, equation of state, and chemical diffusion. Through a statistical assessment, we have derived a confident parameter set as the best solution which minimized $X^{2}$ within the observational error domain. Most of all, we found that 85 Peg is not a binary system but a triple system with an unseen companion 85 Peg $B_{b}\;{\sim}0.16M_{\odot}$. The aim of the present paper is (1) to provide a complete modelling of the stellar system based on the evolutionary theory, and (2) to constrain the physical dimensions such as mass, metallicity and age.
The Evolutionary Statuses of Solar Type Detached Eclipsing Binary Stars
Chanisa Kanjanascul,Kiehunn Bach,Kyeongsoo Hong,Sungeun Kim,Jae-Woo Lee,Young-Woon Kang 한국우주과학회 2012 Journal of Astronomy and Space Sciences Vol.29 No.2
We presented fundamental stellar parameters and evolutionary statuses of six solar type detached eclipsing binaries whose masses are in the range of 0.97-1.43 M⊙. EK Cep and FL Lyr belong to the zero age main sequence. HS Hya, IT Cas and CD Tau are on the main sequence. Their ages are 1.3, 1.9 and 2.2 Gyr, respectively. Both component stars of AI Phe evolved to sub giants and its age is 4.0 Gyr. Those ages of the detached binary systems show good agreement with the time scale for synchronization and circularization of the binary systems.
The Effects of Nitrogen and Oxygen Abundance Variations on The Evolutionary Tracks of Low-Mass Stars
나종삼,이영욱,한상일,박기훈,김용철,Na, Chongsam,Lee, Young-Wook,Han, Sang-Il,Bach, Kiehunn,Kim, Yong-Cheol 한국천문학회 2012 天文學會報 Vol.37 No.2
Recent observations show that there are variations in light elements, such as C, N, O, and Na, between the sub-populations in most globular clusters in the Milky Way. In order to investigate their effects on the evolution of stars in globular clusters, we constructed new sets of isochrones and horizontal branch evolutionary tracks under different assumptions as to the abundance of N and O ([N/Fe] and [O/Fe], respectively). In this talk, we will present our preliminary results from these calculations.